Guinea pig vesicular fluid was characterized both biochemically and immunologically. Biochemical analyses showed this fluid to be homogeneous by ultracentrifugal analyses, revealing a single boundary with a sedimentation coeflicient of 1.5 S. In contrast, electrophoretic separation methods revealed six components, of which three were major components, of approximately equal proportions. They were termed I, II, and III. One of these components (II) was shown to be strongly antigenic in heteroimmunization, whereas components I and III failed to show any antigenicity, even after diverse attempts. This antigen (component II) was found to be highly tissue specific and species specific.
Through procedures of isoimmunization, component II was also found to be immunogenic, giving rise (in male animals) to autoantibodies, A high proportion of injected guinea pigs showed positive skin tests and many revealed tissue lesions when the seminal vesicles were examined histologically. It is therefore concluded that experimental autoimmune disease of the seminal vesicle has been induced.